The present invention concerns an articulated overhead door comprising several panels linked together one after another in the direction of motion. The panels are guided by rollers at each end traveling in two sets of lateral tracks. The first set of tracks has a more or less vertical section that merges into a curved section and then into a horizontal section. The second set of tracks has a horizontal section that merges into a downward-sloping section and then, next to the doorway, into a vertical section. The horizontal section is positioned just over and paralleling the horizontal section of the first set of tracks. All the panels except the one that is uppermost when the door is closed are guided by rollers that travel in the first set of tracks. The panel that is uppermost when the door is closed is guided by rollers at the upper edge. These rollers travel in the second set of tracks. The door is balanced by a mechanism comprising more or less horizontal helical tension springs, deflection rollers, and cables. One end of each spring is secured to a part of the building extending away from the doorway. The other end of each spring, the end extending into the doorway, is fastened to a deflection roller. Each cable is fixed at one end, wraps around a deflection roller, and extends to a point established at one end of the bottom edge of the panel that is lowermost when the door is closed.
Articulated overhead doors are often preferred to unarticulated overhead doors because they require less space inside the building to open and close. They occupy less space above the doorway's lintel than a roll-up door does. They are also easier to handle than vertically or horizontally swinging doors, which require space both inside and sometimes outside the building.
Attempts have been made to get along with less space above the lintel by employing what are called subsidiary tracks for the rollers that guide the panel that is uppermost when the door is closed. Such tracks either extend over the horizontal sections of the tracks that the other panels' rollers travel in or are integrated into them as far as the sections that face and slope down toward the doorway. A door-balancing shaft can be mounted above such sections, and, even though the downward slope helps to provide room for it, a lot of space is still needed above the upper edge of the doorway.
Mounting tension-spring mechanisms above (CH Patent 343 624) of below (U.S. Pat. No. 2,271,309) the horizontal section of the track instead of a torsion-spring shaft behind the lintel has been suggested. This approach, however, demands more overhead space, especially in a garage, or decreases the space at each side and below the horizontal sections of track.